This invention relates to hydrostatic steering systems, and more particularly to steering systems for heavy duty vehicles where substantial fluid flow is required to effect vehicle steering.
A common conventional steering system known in the art is a hydrostatic steering system and typical of hydrostatic steering units utilized in such system is shown in Goff U.S. Pat. No. 3,542,543. In general, such units include a valve which is actuated upon turning of the steering wheel and which then directs fluid from a supply pump through a metering mechainsm to the power steering cylinder to thereby effect steering of the vehicle. The metering mechanism effects a proper follow-up action between the steering wheel and the vehicle wheels so that the vehicle wheels properly turn with turning of the steering wheel. In addition, the metering mechanism in certain systems acts as a pump for effecting steering when the supply pump is not operating to enable manual steering to occur even when the supply pump is inoperative.
In steering systems for effecting steering of large vehicles where a substantial volumetric flow rate is required to effect the steering of the vehicle, the use of the conventional type of hydroststic steering as noted above is not practical, one reason being that the metering means therein must be of a substantial size to handle the necessary flows, which in turn creates problems.